1. Field of the Invention:
The invention relates to a spring winding gearing for the drive assembly of a device, especially a medical infusion apparatus, with a drive shaft biased by a coil spring and a drive controlling means acting on the drive shaft via an intermediate transmission.
2. Description of the Related Art:
Spring winding gearings are used when a part has to be moved regularly for an extended period of time in a mechanical manner and without a current source. This is the case for all kinds of clocks. Further, in an apparatus for continuous infusion, a coil mechanism of the drive assembly serves to advance the plunger of an injection syringe, the advance being controlled by a mechanical clockwork. Such a continuous infusion apparatus is described in U.S. Pat. 4,300,554.
All spring winding gearings or clockwork mechanisms suffer from the disadvantage that, if any part between the spring box and the drive controlling means beaks, the drive assembly rapidly races without control. This is because the coil spring, once disengaged from the drive controlling means, can freely relieve, thus releasing the stored energy at once. Of course, this effect is undesired in every kind of application of a spring winding gearing. In a continuous infusion apparatus or a similar medical apparatus this effect is angerous because the highly effective endogenous chemical substance and the medicament, respectively, which is contained in the injection syringe, can be entirely injected into the blood vessel system of a patient suddenly, instead of being continuously administered in small doses over an extended period of time.